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The '''Whirlpool Galaxy''', also known as '''Messier 51a''', '''M51a''', and '''NGC 5194''', is an ]<ref name="arp1966"> The '''Whirlpool Galaxy''', also known as '''Messier 51a''', '''M51a''', and '''NGC 5194''', is an ] ] ] with a ] ].<ref name="elmegreenelmegreen1987">
{{cite journal {{cite journal
| first=H. |last=Arp | first=H. |last=Arp
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| bibcode=1966ApJS...14....1A | bibcode=1966ApJS...14....1A
| doi=10.1086/190147 | doi=10.1086/190147
⚫ }}</ref>
}}</ref> ]<ref name="elmegreenelmegreen1987">
{{cite journal <ref name="arp1966">{{cite journal
| first=D. M. |last=Elmegreen |first2=B. G. |last2=Elmegreen | first=D. M. |last=Elmegreen |first2=B. G. |last2=Elmegreen
| date=1987 | date=1987
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| bibcode=1987ApJ...314....3E | bibcode=1987ApJ...314....3E
| doi=10.1086/165034 | doi=10.1086/165034
}}</ref> ] with a ] ]<ref name=A>{{cite journal |last=Matsushita |first=Satoki |last2=Muller |first2=Sebastien |last3=Lim |first3=Jeremy |date=9 April 2007 |title=Jet-disturbed molecular gas near the Seyfert 2 nucleus in M51 |journal= |publisher= |volume= |issue=A&A Letters Special Issue |pages= |doi=10.1051/0004-6361:20067039 |arxiv = 0704.0947 |bibcode = 2007A&A...468L..49M }}</ref> in the ] ]. It was the first galaxy to be classified as a spiral galaxy.<ref>{{cite web|title=Whirlpool Galaxy: First Spiral Galaxy|url=http://www.universeforfacts.com/2012/04/whirlpool-galaxy-first-spiral-galaxy.html|website=Universe for Facts|accessdate=21 December 2014}}</ref> Recently it was estimated to be 23 ± 4 million ]s from the ],<ref name="Tak´atsetal2006" /> but different methods yield distances between 15 and 35 million light-years. Messier 51 is one of the best known galaxies in the sky.<ref> }}</ref><ref name=A>{{cite journal |last=Matsushita |first=Satoki |last2=Muller |first2=Sebastien |last3=Lim |first3=Jeremy |date=9 April 2007 |title=Jet-disturbed molecular gas near the Seyfert 2 nucleus in M51 |journal= |publisher= |volume= |issue=A&A Letters Special Issue |pages= |doi=10.1051/0004-6361:20067039 |arxiv = 0704.0947 |bibcode = 2007A&A...468L..49M }}</ref> It lies in the ] ], and was the first galaxy to be classified as a spiral galaxy.<ref>{{cite web|title=Whirlpool Galaxy: First Spiral Galaxy|url=http://www.universeforfacts.com/2012/04/whirlpool-galaxy-first-spiral-galaxy.html|website=Universe for Facts|accessdate=21 December 2014}}</ref> Its distance is estimated to be between 15 and 35 million light-years.<ref name="Tak´atsetal2006" />

{{cite book
⚫ The galaxy and its companion, ],<ref>https://messierobjects101.com/messier-object-m51/</ref> are easily observed by ], and the two galaxies may be seen with ].<ref name=apod>
| last=Scalzi |first=John
| date=2003
| title=The Rough Guide to the Universe
| publisher=]
| pages=250
| isbn=1-85828-939-4
⚫ }}</ref>
⚫ The galaxy and its companion, ],<ref>https://messierobjects101.com/messier-object-m51/</ref> are easily observed by ], and the two galaxies may even be seen with ].<ref name=apod>
{{Cite APOD {{Cite APOD
|date=2000-07-24 |date=2000-07-24
|title=M51: The Whirlpool Galaxy |title=M51: The Whirlpool Galaxy
|access-date=2007-04-22 |access-date=2007-04-22
}}</ref> The Whirlpool Galaxy is also a popular target for professional astronomers, who study it to further understand galaxy structure (particularly structure associated with the ]) and galaxy interactions. }}</ref> The Whirlpool Galaxy has been extensively observed by professional astronomers, who study it to understand galaxy structure (particularly structure associated with the ]) and galaxy interactions.


==Discovery== ==Discovery==
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|title=Connaissance des Temps |title=Connaissance des Temps
|pages=227–267 |pages=227–267
}}</ref> Its companion galaxy, ], was discovered in 1781 by ], although it was not known whether it was interacting or merely another galaxy passing at a distance. It was, however, not until 1845 that ], employing a 72-inch (1.8 m) ] at ], Ireland, found the Whirlpool possessed a ], the first "nebula" to be known to have one. These "]e" were not recognized as galaxies until ] was able to observe ]s in some of these spiral nebulae, which provided evidence that they were so far away that they must be entirely separate galaxies.<ref> }}</ref> Its companion galaxy, ], was discovered in 1781 by ], although it was not known whether it was interacting or merely another galaxy passing at a distance. In 1845, ], employing a 72-inch (1.8 m) ] at ], Ireland, found the Whirlpool possessed a ], the first "nebula" to be known to have one. These "]e" were not recognized as galaxies until ] was able to observe ]s in some of these spiral nebulae, which provided evidence that they were so far away that they must be entirely separate galaxies.<ref>
{{cite journal {{cite journal
|last1=Hubble |first1=E. P. |last1=Hubble |first1=E. P.
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Located within the constellation ], M51 is found by following the easternmost star of the ], ], and going 3.5° southwest. Its declination is +47°, making it a ] for observers located above 43°N latitude; it reaches high altitudes throughout the northern hemisphere making it an accessible object from the early hours in winter through the end of spring season, after which observation is hindered in lower latitudes.{{Citation needed|date=June 2011}} Located within the constellation ], M51 is found by following the easternmost star of the ], ], and going 3.5° southwest. Its declination is +47°, making it a ] for observers located above 43°N latitude; it reaches high altitudes throughout the northern hemisphere making it an accessible object from the early hours in winter through the end of spring season, after which observation is hindered in lower latitudes.{{Citation needed|date=June 2011}}


M51 is visible through ] under ] and can be resolved in detail with modern amateur telescopes.<ref name="apod" /> When seen through a 100&nbsp;mm telescope the basic outlines of M51 (limited to 5x6') and its companion are visible. Under dark skies, and with a moderate eyepiece through a 150&nbsp;mm telescope, M51's intrinsic spiral structure can be detected. With larger (>300&nbsp;mm) instruments under dark sky conditions, the various spiral bands are apparent with ]s visible, and M51 can be seen to be attached to ]. M51 is visible through ] under dark sky conditions, and it can be resolved in detail with modern amateur telescopes.<ref name="apod" /> When seen through a 100&nbsp;mm telescope the basic outlines of M51 (limited to 5x6') and its companion are visible. Under dark skies, and with a moderate eyepiece through a 150&nbsp;mm telescope, M51's intrinsic spiral structure can be detected. With larger (>300&nbsp;mm) instruments under dark sky conditions, the various spiral bands are apparent with ]s visible, and M51 can be seen to be attached to ].


As is usual for galaxies, the true extent of its structure can only be gathered from inspecting photographs; long exposures reveal a large nebula extending beyond the visible circular appearance. As is usual for galaxies, the true extent of its structure can only be gathered from inspecting photographs; long exposures reveal a large nebula extending beyond the visible circular appearance.
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] ]


With the recent SN 2005cs derived estimate of 23 Mly distance, and an angular diameter of roughly 11.2&prime;, it can be inferred that M51's bright circular disk has a radius of about 43,000 light-years. Overall the galaxy is about 35% the size of the ]. Its ] is estimated to be 160 billion solar masses. With the distance estimate for SN 2005cs of 23 million light years, and an angular diameter of roughly 11.2 ]s, it can be inferred that M51's bright circular disk has a radius of about 43,000 light-years.{{or}} Overall the galaxy is about 35% the size of the ]. Its ] is estimated to be 160 billion solar masses.{{fact}}


A ], surrounded by a ring of dust, is thought to exist at the heart of the spiral. The dust ring stands almost perpendicular to the relatively flat spiral nebula. A secondary ring crosses the primary ring on a different axis, a phenomenon that is contrary to expectations. A pair of ]s extend from the axis of the main dust ring.<ref>{{cite web | date=June 8, 1992 | url=http://hubblesite.org/newscenter/newsdesk/archive/releases/1992/17/text/ | title=NASA's Hubble Space Telescope Resolves a Dark "x" Across the Nucleus of M51 | work=News Center | publisher=HubbleSite | accessdate=August 7, 2006 }}</ref> A ], surrounded by a ring of dust, is thought to exist at the heart of the spiral. The dust ring stands almost perpendicular to the relatively flat spiral nebula. A secondary ring crosses the primary ring on a different axis, a phenomenon that is contrary to expectations. A pair of ]s extend from the axis of the main dust ring.<ref>{{cite web | date=June 8, 1992 | url=http://hubblesite.org/newscenter/newsdesk/archive/releases/1992/17/text/ | title=NASA's Hubble Space Telescope Resolves a Dark "x" Across the Nucleus of M51 | work=News Center | publisher=HubbleSite | accessdate=August 7, 2006 }}</ref>


===Spiral structure=== ===Spiral structure===
The very pronounced spiral structure of the Whirlpool Galaxy is believed to be the result of the close interaction between it and its companion galaxy ]; specifically, its passing through the main disk of M51 about 500 to 600 million years ago. In this model,<ref name="Salo & Laurikainen"> The pronounced spiral structure of the Whirlpool Galaxy is believed to be the result of the close interaction between it and its companion galaxy ], which may have passed through the main disk of M51 about 500 to 600 million years ago. In this proposed scenario, ] came from behind M51 through the disk towards the observer and made another disk crossing as recently as 50 to 100 million years ago until it is where we observe it to be now, slightly behind M51.<ref name="Salo & Laurikainen">
{{cite journal {{cite journal
| last=Salo |first=Heikki |last2=Laurikainen |first2=Eija | last=Salo |first=Heikki |last2=Laurikainen |first2=Eija
Line 131: Line 124:
| bibcode=1999Ap&SS.269..663S | bibcode=1999Ap&SS.269..663S
| doi=10.1023/A:1017002909665 | doi=10.1023/A:1017002909665
}}</ref>
}}</ref> ] came from behind M51 through the disk towards the observer and made another disk crossing as recently as 50 to 100 million years ago until it is where we observe it to be now, slightly behind M51.


===Star formation=== ===Star formation===
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When this happens, these new-born stars consume huge amounts of gas causing them to expand, shine even hotter, and finally sweep away the surrounding layers of dust and gas by increasing efflux of the stellar wind. The gigantic proportions of the clouds out of which they are born means stars seldom, if ever, are created in isolation. Thus regions of several hot young stars emit sufficient light energy that they can be seen in the high resolution pictures of M51 across millions of lightyears distance. When this happens, these new-born stars consume huge amounts of gas causing them to expand, shine even hotter, and finally sweep away the surrounding layers of dust and gas by increasing efflux of the stellar wind. The gigantic proportions of the clouds out of which they are born means stars seldom, if ever, are created in isolation. Thus regions of several hot young stars emit sufficient light energy that they can be seen in the high resolution pictures of M51 across millions of lightyears distance.

For an example of such a formation in our own galaxy, see M16, the ].


===Transient events=== ===Transient events===
{{As of|2016|February}}, three supernovae have been observed in the Whirlpool Galaxy so far.<ref>{{cite web | url=http://www.cbat.eps.harvard.edu/lists/Supernovae.html | title=List of Supernovae | publisher=Central Bureau for Astronomical Telegrams | accessdate=February 27, 2016}}</ref> In 1994, ] ] was observed in the Whirlpool Galaxy. It was classified as Ic and its brightness peaked at ] 12.91. Three ]e have been observed in the Whirlpool Galaxy.<ref>{{cite web | url=http://www.cbat.eps.harvard.edu/lists/Supernovae.html | title=List of Supernovae | publisher=Central Bureau for Astronomical Telegrams | accessdate=February 27, 2016}}</ref> In 1994, ] was observed in the Whirlpool Galaxy. It was classified as ], indicating that its progenitor star was very massive and had already shed much of its mass, and its brightness peaked at ] 12.91.


In June 2005 the type II supernova ] was observed in the Whirlpool Galaxy, peaking at ] 14.<ref>{{cite web | last=MacRobert | first=Alan M. | date=August 24, 2005 | url=http://skyandtelescope.com/news/article_1544_1.asp | title=Supernova in M51 | work=Sky Tonight | publisher=Sky and Telescope | accessdate=August 7, 2006 }}</ref><ref>{{cite web |last=Bishop | first=David | url=http://www.supernovae.net/sn2005/sn2005cs.html | title=Supernova 2005cs in M51 | work=supernovae.net |accessdate=August 7, 2006 }}</ref> In June 2005 the type II supernova ] was observed in the Whirlpool Galaxy, peaking at ] 14.<ref>{{cite web | last=MacRobert | first=Alan M. | date=August 24, 2005 | url=http://skyandtelescope.com/news/article_1544_1.asp | title=Supernova in M51 | work=Sky Tonight | publisher=Sky and Telescope | accessdate=August 7, 2006 }}</ref><ref>{{cite web |last=Bishop | first=David | url=http://www.supernovae.net/sn2005/sn2005cs.html | title=Supernova 2005cs in M51 | work=supernovae.net |accessdate=August 7, 2006 }}</ref>


On 31 May 2011 a ], was detected in the Whirlpool Galaxy, peaking at magnitude 12.1.<ref name="supernovae.net">{{cite web On 31 May 2011 a ] was detected in the Whirlpool Galaxy, peaking at magnitude 12.1.<ref name="supernovae.net">{{cite web
|title=Supernovae 2011dh in M51 |title=Supernovae 2011dh in M51
|publisher=supernovae.net (International Supernovae Network) |publisher=supernovae.net (International Supernovae Network)
|first=David |last=Bishop |first=David |last=Bishop
|url=http://www.rochesterastronomy.org/sn2011/sn2011dh.html |url=http://www.rochesterastronomy.org/sn2011/sn2011dh.html
|accessdate=2011-06-06 }}</ref> This supernova, designated ], showed a spectrum much bluer than average, with ] like characteristics in its ].<ref name="AAVSO">{{cite web |accessdate=2011-06-06 }}</ref> This supernova, designated ], showed a spectrum much bluer than average, with ] profiles, which indicate rapidly expanding material, in its ].<ref name="AAVSO">{{cite web
|date=2011-06-03 |date=2011-06-03
|title=AAVSO Special Notice #241: New Supernova in M51 |title=AAVSO Special Notice #241: New Supernova in M51
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|first=Richard |last=Kinne (kqr) |first=Richard |last=Kinne (kqr)
|url=http://www.aavso.org/aavso-special-notice-241 |url=http://www.aavso.org/aavso-special-notice-241
|accessdate=2011-06-06 }}</ref> Interestingly, the progenitor was probably a ]<ref name="atel3401">{{cite web |accessdate=2011-06-06 }}</ref> The progenitor was probably a ]<ref name="atel3401">{{cite web
|date=2011-06-03 |date=2011-06-03
|title=ATEL 3401: Properties of the Candidate Progenitor of SN 2011dh in M51 |title=ATEL 3401: Properties of the Candidate Progenitor of SN 2011dh in M51
|publisher=Astronomers Telegram |url=http://www.astronomerstelegram.org/?read=3401 |publisher=Astronomers Telegram |url=http://www.astronomerstelegram.org/?read=3401
|accessdate=2011-06-06 }}</ref> and not a ] or ], which is unusual. |accessdate=2011-06-06 }}</ref> and not a ] or ], which are thought to be the most common supernova progenitors.


==Companion== ==Companion==
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] photo of M51 taken with amateur ] equipment]] ] photo of M51 taken with amateur ] equipment]]


] (also known as Messier 51b or M51b) is a dwarf galaxy that is interacting with the Whirlpool Galaxy (also known as M51a or NGC 5194). Both galaxies are located approximately 25 million light-years away in the constellation Canes Venatici. Together, the two galaxies are one of the most famous interacting galaxy pairs. ] (also known as Messier 51b or M51b) is a dwarf galaxy that is interacting with the Whirlpool Galaxy (also known as M51a or NGC 5194). Both galaxies are located approximately 25 million light-years away in the constellation Canes Venatici. Together, the two galaxies are one of the most widely studied interacting galaxy pairs.


==Galaxy group information== ==Galaxy group information==

Revision as of 08:32, 9 December 2017

Whirlpool Galaxy
Whirlpool Galaxy (M51A or NGC 5194). The smaller object in the upper right is M51B or NGC 5195. Credit: NASA/ESA
Observation data (J2000 epoch)
ConstellationCanes Venatici
Right ascension13 29 52.7
Declination+47° 11′ 43″
Redshift463 ± 3 km/s
Distance23.000 Mly (7.1 ± 1.2 Mpc)
Apparent magnitude (V)8.4
Characteristics
TypeSA(s)bc pec
Size~60,000ly in diameter
Apparent size (V)11′.2 × 6′.9
Notable featuresInteracting with NGC 5195
Other designations
Question Mark Galaxy, Rosse's Galaxy, M51a, NGC 5194, UGC 8493, PGC 47404, VV 001a, VV 403, Arp 85, GC 3572

The Whirlpool Galaxy, also known as Messier 51a, M51a, and NGC 5194, is an interacting grand-design spiral galaxy with a Seyfert 2 active galactic nucleus. It lies in the constellation Canes Venatici, and was the first galaxy to be classified as a spiral galaxy. Its distance is estimated to be between 15 and 35 million light-years.

The galaxy and its companion, NGC 5195, are easily observed by amateur astronomers, and the two galaxies may be seen with binoculars. The Whirlpool Galaxy has been extensively observed by professional astronomers, who study it to understand galaxy structure (particularly structure associated with the spiral arms) and galaxy interactions.

Discovery

Sketch of M51 by Lord Rosse in 1845.

What later became known as the Whirlpool Galaxy was discovered on October 13, 1773, by Charles Messier while hunting for objects that could confuse comet hunters, and was designated in Messier's catalogue as M51. Its companion galaxy, NGC 5195, was discovered in 1781 by Pierre Méchain, although it was not known whether it was interacting or merely another galaxy passing at a distance. In 1845, William Parsons, 3rd Earl of Rosse, employing a 72-inch (1.8 m) reflecting telescope at Birr Castle, Ireland, found the Whirlpool possessed a spiral structure, the first "nebula" to be known to have one. These "spiral nebulae" were not recognized as galaxies until Edwin Hubble was able to observe Cepheid variables in some of these spiral nebulae, which provided evidence that they were so far away that they must be entirely separate galaxies.

The advent of radio astronomy and subsequent radio images of M51 unequivocally demonstrated that the Whirlpool and its companion galaxy are indeed interacting. Sometimes the designation M51 is used to refer to the pair of galaxies, in which case the individual galaxies may be referred to as M51A (NGC 5194) and M51B (NGC 5195).

Visual appearance

The image of the Whirlpool Galaxy in visual light (left) and infrared light (right).

Located within the constellation Canes Venatici, M51 is found by following the easternmost star of the Big Dipper, Eta Ursae Majoris, and going 3.5° southwest. Its declination is +47°, making it a circumpolar for observers located above 43°N latitude; it reaches high altitudes throughout the northern hemisphere making it an accessible object from the early hours in winter through the end of spring season, after which observation is hindered in lower latitudes.

M51 is visible through binoculars under dark sky conditions, and it can be resolved in detail with modern amateur telescopes. When seen through a 100 mm telescope the basic outlines of M51 (limited to 5x6') and its companion are visible. Under dark skies, and with a moderate eyepiece through a 150 mm telescope, M51's intrinsic spiral structure can be detected. With larger (>300 mm) instruments under dark sky conditions, the various spiral bands are apparent with HII regions visible, and M51 can be seen to be attached to M51B.

As is usual for galaxies, the true extent of its structure can only be gathered from inspecting photographs; long exposures reveal a large nebula extending beyond the visible circular appearance.

In January 2005 the Hubble Heritage Project constructed a 11477 × 7965-pixel composite image (shown in the infobox above) of M51 using Hubble's ACS instrument. The image highlights the galaxy's spiral arms, and shows detail into some of the structures inside the arms.

Properties

A 1992 Hubble image showing a knot of dust once thought to be a pair of rings encircling a black hole.
A 2005 Hubble image showing details of the dust at the nucleus of M51.

With the distance estimate for SN 2005cs of 23 million light years, and an angular diameter of roughly 11.2 arcminutes, it can be inferred that M51's bright circular disk has a radius of about 43,000 light-years. Overall the galaxy is about 35% the size of the Milky Way. Its mass is estimated to be 160 billion solar masses.

A black hole, surrounded by a ring of dust, is thought to exist at the heart of the spiral. The dust ring stands almost perpendicular to the relatively flat spiral nebula. A secondary ring crosses the primary ring on a different axis, a phenomenon that is contrary to expectations. A pair of ionization cones extend from the axis of the main dust ring.

Spiral structure

The pronounced spiral structure of the Whirlpool Galaxy is believed to be the result of the close interaction between it and its companion galaxy NGC 5195, which may have passed through the main disk of M51 about 500 to 600 million years ago. In this proposed scenario, NGC 5195 came from behind M51 through the disk towards the observer and made another disk crossing as recently as 50 to 100 million years ago until it is where we observe it to be now, slightly behind M51.

Star formation

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Stars are usually formed in the center of the galaxy. The center part of M51 appears to be undergoing a period of enhanced star formation. The present efficiency of star formation, defined as the ratio of mass of new stars to the mass of star-forming gas, is only ~1%, quite comparable to the global value for the Milky Way and other galaxies. It is estimated that the current high rate of star formation can last no more than another 100 million years or so.

Induced spiral structure in the larger galaxy is not the only effect of the interaction. Significant compression of hydrogen gas occurs that leads to the development of starbirth regions. In pictures of M51 these show up as the bright blue 'knots' throughout the spiral arms.

Generally speaking, hydrogen gas is the most common component of the interstellar medium (the vast space between stars and planetary systems in galaxies). It exists primarily in its atomic structure and molecular form, and forms huge clouds throughout the entire galaxy. When large sources of gravitational pull pass nearby, such as other galaxies, gravitational interactions produce compression (density) waves that sweep through these hydrogen clouds. This causes some regions of the previously diffuse gas to compress into tight pockets of opaque and dense gas; these are dust lanes one so often sees in the spiral arms. In regions where the concentration and density of gas reaches a critical value, further collapse under its own gravitational pull occurs, and stars are born at the center of the collapse, where the gas is compressed so strongly that fusion initiates.

When this happens, these new-born stars consume huge amounts of gas causing them to expand, shine even hotter, and finally sweep away the surrounding layers of dust and gas by increasing efflux of the stellar wind. The gigantic proportions of the clouds out of which they are born means stars seldom, if ever, are created in isolation. Thus regions of several hot young stars emit sufficient light energy that they can be seen in the high resolution pictures of M51 across millions of lightyears distance.

Transient events

Three supernovae have been observed in the Whirlpool Galaxy. In 1994, SN 1994I was observed in the Whirlpool Galaxy. It was classified as type Ic, indicating that its progenitor star was very massive and had already shed much of its mass, and its brightness peaked at apparent magnitude 12.91.

In June 2005 the type II supernova SN 2005cs was observed in the Whirlpool Galaxy, peaking at apparent magnitude 14.

On 31 May 2011 a type II supernova was detected in the Whirlpool Galaxy, peaking at magnitude 12.1. This supernova, designated SN 2011dh, showed a spectrum much bluer than average, with P Cygni profiles, which indicate rapidly expanding material, in its hydrogen-Balmer lines. The progenitor was probably a yellow supergiant and not a red or blue supergiant, which are thought to be the most common supernova progenitors.

Companion

Main article: NGC 5195
Widefield photo of M51 taken with amateur astrophotography equipment

NGC 5195 (also known as Messier 51b or M51b) is a dwarf galaxy that is interacting with the Whirlpool Galaxy (also known as M51a or NGC 5194). Both galaxies are located approximately 25 million light-years away in the constellation Canes Venatici. Together, the two galaxies are one of the most widely studied interacting galaxy pairs.

Galaxy group information

Main article: M51 Group

The Whirlpool Galaxy is the brightest galaxy in the M51 Group, a small group of galaxies that also includes M63 (the Sunflower Galaxy), NGC 5023, and NGC 5229. This small group may actually be a subclump at the southeast end of a large, elongated group that includes the M101 Group and the NGC 5866 Group, although most group identification methods and catalogs identify the three groups as separate entities.

See also

References

  1. Dreyer, J. L. E. (1988). Sinnott, R. W. (ed.). The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters. Sky Publishing Corporation/Cambridge University Press. ISBN 0-933346-51-4.
  2. ^ "NASA/IPAC Extragalactic Database". Results for NGC 5194. Retrieved 2006-12-06.
  3. ^ Takáts, K.; Vinkó, J. (2006). "Distance estimate and progenitor characteristics of SN 2005cs in M51". Monthly Notices of the Royal Astronomical Society. 372 (4): 1735. arXiv:astro-ph/0608430. Bibcode:2006MNRAS.372.1735T. doi:10.1111/j.1365-2966.2006.10974.x.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  4. "Distance Results for MESSIER 051". NASA/IPAC Extragalactic Database. Retrieved 2011-06-06.
  5. "M51". SEDS.org.
  6. http://www.nasa.gov/multimedia/imagegallery/image_feature_2457.html#.VIX_OGf0DDE Retrieved Dec-2014
  7. ^ Elmegreen, D. M.; Elmegreen, B. G. (1987). "Arm classifications for spiral galaxies". Astrophysical Journal. 314: 3–9. Bibcode:1987ApJ...314....3E. doi:10.1086/165034.
  8. Arp, H. (1966). "Atlas of Peculiar Galaxies". Astrophysical Journal Supplement. 14: 1–20. Bibcode:1966ApJS...14....1A. doi:10.1086/190147.
  9. Matsushita, Satoki; Muller, Sebastien; Lim, Jeremy (9 April 2007). "Jet-disturbed molecular gas near the Seyfert 2 nucleus in M51" (A&A Letters Special Issue). arXiv:0704.0947. Bibcode:2007A&A...468L..49M. doi:10.1051/0004-6361:20067039. {{cite journal}}: Cite journal requires |journal= (help)
  10. "Whirlpool Galaxy: First Spiral Galaxy". Universe for Facts. Retrieved 21 December 2014.
  11. https://messierobjects101.com/messier-object-m51/
  12. ^ Nemiroff, R.; Bonnell, J., eds. (2000-07-24). "M51: The Whirlpool Galaxy". Astronomy Picture of the Day. NASA. Retrieved 2007-04-22.
  13. Messier, Charles (1781). "Catalogue des Nébuleuses & des amas d'Étoiles". Connaissance des Temps . pp. 227–267 .
  14. Hubble, E. P. (1929). "A spiral nebula as a stellar system, Messier 31". Astrophysical Journal. 69: 103–158. Bibcode:1929ApJ....69..103H. doi:10.1086/143167.
  15. "Out of This Whirl: the Whirlpool Galaxy (M51) and Companion Galaxy". News Center. HubbleSite. April 25, 2005. Retrieved August 7, 2006.
  16. "NASA's Hubble Space Telescope Resolves a Dark "x" Across the Nucleus of M51". News Center. HubbleSite. June 8, 1992. Retrieved August 7, 2006.
  17. Salo, Heikki; Laurikainen, Eija (1999). "A Multiple Encounter Model of M51". Astrophysics and Space Science. 269: 663–664. Bibcode:1999Ap&SS.269..663S. doi:10.1023/A:1017002909665.
  18. Thronson, Harley A.; Greenhouse, Matthew A. (1988). "Near-Infrared Mass-to-light ratios in Galaxies: Stellar Mass and Star Formation in the Heart of the Whirlpool". The Astrophysical Journal. 327: 671–679. Bibcode:1988ApJ...327..671T. doi:10.1086/166224.
  19. Kaler, James B (2001). The Little Book of Stars. New York, NY: Copernicus Books. p. 21. ISBN 0-387-95005-2.
  20. "List of Supernovae". Central Bureau for Astronomical Telegrams. Retrieved February 27, 2016.
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  22. Bishop, David. "Supernova 2005cs in M51". supernovae.net. Retrieved August 7, 2006.
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External links

Astronomical catalogs
Messier
NGC
PGC
UGC
Arp
GC


Messier objects
List Painting of Charles Messier, creator of the Messier catalog
See also
New General Catalogue 5000 to 5499
List of notable Seyfert galaxies
Seyfert 1
Seyfert 2
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